Cathode-ray tube



Jan. 6, 1942. s. J. KOCH CATHODE-RAY TUBE Filed Nov. 12, 1940 5Sheets-Sheet l INVENTOR (qyd 06A Jan. 6, 1942. J, KOCH CATHODE-RAY TUBEFiled Nov'. 12, 1940 3 Sheets-Sheet 2 Jan. 6, 1942. 5, J CH 2,269,115

CATHODE-RAY TUBE Filed Nov. 12, 1940 3 Sheets-Sheet 3 SECONDACCELERATINQ ELECTRODE +Sooov.

FOCUS\NG awe-meme +\5oov.

FlRST AcceLeRA-rmq ELECTRODE +snoov.

. INVENTOR g0 Sfqzzgy 06% MODULATWG ELECTRODE CATHODE'.

Patented Jan. 6, 1942 CATHODE-RAY TUBE Stanley J. Koch, Newark, N. J.,asslgnor to Allen B. Du Mont Laboratories, Inc., Passaic, N. .L, acorporation of Delaware Application November 12, 1940, Serial No.365,216

7 Claims.

My invention relates to improvements in cathode-ray tubes of the generaltype more particularly adapted for television reception, and such as isdisclosed in Patent No. 2,186,635 issued Janu- Heretofore, theimportance of electrode position, and size, shape and spacing of thesame,

have been overlooked in cathode-ray tubes of the prior, general typereferred to. As a result, the

ary 9, 1940 to Allen B. Du Mont and Alfred J. uses to which such tubescan be put, and the Hinck, Jr., and Patent No. 2,225,099, issuedDetheoretical advantages to be enjoyed with cercember 17, 1940, to PeterS. Christaldi. tain types of operation, are sharply curtailed.

As a result of development of the so-called Inorder to gain highintensity, while maintain- Braun tube for television reception, it hasbeen in high-deflection sensitivity, it is desirable to definitelydetermined that certain values, 10 make as large as possible the ratioof post-acwhether they be of operating potentials on cerceleration topre-acceleration potential. It has tain electrodes, or of dimensions inthe tube been found that unless certain designs are apstructure itself,must be properly correlated in plied, defocusing of the fluorescent spotoccurs, order to obtain the desired operating action. For distortingfields are set up, and it may be imexample, it is known that byincreasing the op- 1 possible to utilize more than thirty percent of theerating potential on an accelerating anode of a efiective fluorescentscreen area. conventional cathode-ray tube, the intensity or With theforegoing in mind, it is one of the brightness of the trace or pictureis increased. A objects of my invention to provide an improved point orpotential range is finally reached, howconstruction of cathode-ray tubeof the charever, whereat the sensitivity of deflection is reacterreferred to in which the operating potenduced a prohibitive amount, sothatit is not tials, and dimensions in the tube structure itself,practical to further increase the brightness of the are such that apicture of the desired brightness picture by this method alone. Anotherdiificulty on the fluorescent screen can be obtained without has beenfound to reside in the matter of mainnecessarily or unduly interferingwith the focus taining the scanning electron ray at a good focus or thesensitivity of deflection. on the fluorescent screen. That is, in makingAnother object of my invention resides in the certain changes orvariations in some of the opprovision of an improved construction ofcathodeerating potentials or in the structure of the tube ray tube ofthe character referred to, which has itself to correct for or improveupon certain opadvantages over those proposed heretofore in the cratingconditions, the result has been to impair, 'way of a brighter or moreintense picture on the at the same time, the operating action in otherfluorescent screen for similar operating condiways, such as by causingsome form of distortion tions, higher picture detail, greater uniformityof of the pattern or by causing some degree of dethe pattern, greatersimplicity of construction focusing of the electron ray on thefluorescent and of assembly in manufacturing, and more screen. Alon withthis development work, the favorable disposition of the various partsand subject of electron optics has been given conleads with respect toeach other to withstand the siderable attention, in an attempt toformulate high difierences of potential within the tube. some workingbasis or formulae for use in the Another object of my invention residesin the most efiicient design of cathode-ray tubes for provision of asimplified construction for a cathtelevision reception. In putting thistheoretical 40 ode-ray tube in which there is post-deflectioninformation to practice, however, it has been found that there are stilllimitations in the way of an occurring decrease in efiiciency ofoperationof the tube in one important sense if certain acceleration ofthe electron beam or ray, and which overcomes the disadvantages and thlimitations of the various designs proposed heretofore. are maids tocause an Increase m 43 Other objects and advantages will hereinafterciency of operation of the tube in another sense. appear Many differenttypes of cathode-ray tubes have been constructed in which there ispostdefiection acceleration of the electron beam. In most of thesevarious constructions, however, an elaborate system of electrodes hasbeen necessary which makes these tubes impractical. A simplifiedconstruction or system, employing a single electrode in the form of aring disposed in proximity to the fluorescent screen, is disclosed inthe Patent 2,186,635 referred to above. This novel construction makesfeasible commercial production of cathode-ray tubes having the desiredoperating characteristics referred to.

For the purpose of illustrating my invention, an embodiment thereofisshown in the drawings, wherein Figure 1 is an enlarged, fragmentaryview taken from Fig. 10, and being partly broken away, partly inelevation, and partly in section, the section being taken on the line llin Fig. 2;

Fig. la is a detail, fragmentary view, partly in section andillustrative of a novel step in the assembly of my improved cathode-raytube, in some cases;

. Fig. 2 is a view looking toward the right in Fig. 1, the electron gunbeing shown in elevation and '66, 8-3 and -3 in Flam-1 and 2; and

each being a true projection taken vertically from Fig. 1, but on theenlarged scale;

Fig. 4a is an enlarged, fragmentary, sectional:

view showing a detail of my improved construc-- tion, the section beingtaken in th plane 4-4 in Fig. 1;

horizontal N Fig. 10 is a longitudinal, sectional viewer a completecathode-ray tube constructed and operating in accordance with myinvention, the electron gun'and associated parts being shown 8 18-11"vation; and

Fig. 11 is an enlarged view taken from and showing more clearly theelectrodes comprisfing the electron gun. g

The drawings show a cathode-ray tube having a gun construction similarto that described inthe patents mentioned above. For convenience ofcomparison, the various parts have been designated by the same referencecharacters as the corresponding and respective parts in these priordisclosures. r I

With reference particularly to Figs. 1, 2, 10 and 11, my improvedcathode-ray tube comprises a tube l0 having a bulbous portion II on theend wall of which is a fluorescent screen 9. In the neck portion l2 ofthe tube is the gun for developing the ray of electrons directed at andfocused on the screen.

The gun is supported from the stem I5 which is sealed to the open end ofthe neck i2, and comprises a cathode IS, a modulating electrode 20 inwhich the cathode I6 is disposed, a first acceleratingelectrode 22, anda mica disc 24. f

The gun comprises further a focusing electrade 29, 29a and a secondaccelerating electrode 30 provided with the apertured discs 30a and 30b.Deflecting plates 33 are supported by the wires 3311/3312. 33c and 33d,and a second set of deflecting plates 36 is supported by the wires 36a,

36b, 36c and 36d.

The first or preaccelerating electrode 22 above the modulating electrode20 is operated at the same voltage asthe second accelerating electrode30. For this purpose, a connection 42 is made from the electrode 30 tothe electrode 20. By applying a high voltage to the electrode *22; abrighter spot is obtained, and there is less tendency to defocus duringmodulation.

In my improved construction, there is a relatively large distance A fromthe tip 41 of the gun to the adjacent edges 48 of the second set ofdeflecting plates 36. The relation exists approximately, where A ismeasured in inches, C is the diameter in inches of the fluorescentscreen, and B is the distance in inches from the screen to the adjacentedges 49 of the first set of deflecting plates 33. Satisfactory resultshave been obtained by making A equal to .4 inch with C and B both 14inches. In the constructions used heretofore, the distance A is muchless. By making the distance A greater, and using the relation aboveexpressed, defocusing of the spot during deflection is eliminated. The

reason for this is that in my improved construction no appreciablebending or deflection of the beam or ray within the gun structure takesplace.

Heretofore it has been generally supposed that no motion or deflectionof the ray occurs below the deflecting plates. Actually, this is nottrue, and the motion of the ray in the gun during defiection has beenthe cause of poor focusing in the prior constructions.

Important and novel characteristics of my improved tube reside in theprovision of the electrodes 58 and. 59, which may be in the form ofsilver coatings on the inside surface of the tube l0, and in thedimensions and relations hereinafter specified. By this means, it ispossible with my'improved tube to obtain a very intense trace or pictureby using an extremely high final accelerating voltage, but without, atthe same time,

reducing the deflection sensitivity by about 50%,

when the final accelerating voltage is doubled, for example, as would bethe case in the various television'receiver tubes used heretofore, Thereason for this is that in my improved tube the deflection sensitivityis not an inverse function of final accelerating voltage or potential,as is the case in tubes of the prior art.

' .In a practical construction of my improved .tube, the outsidediameter of the neck portion I 2 was made 2% inches, the distancebetween the edges 58a and 59b of the ring electrode" was made twoinches, the distance between the edges 59a and "(1 was made 1 /2 inches,and the distance between the edges 58d and 580 was made one inch.

, In the case of my improved tube, a potential of say 10,000 volts canbe applied to the top electrode 58, 5,000 volts to the electrode 30, anda picture intensity corresponding to 10,000 volts will be obtainedaccordingly, but instead of cutting down the deflection sensitivitybyabout 50% as heretofore, it is only reduced by approximately 18% in mytube.

In the sizes of tubes commonly referred to as a 20 inch" tube, and a "14inch" tube, respectively, the following dimensions, relations and valueshave been found to give very satisfactory results.

In either case, Y may be made equal to Z.

In either case, with E from 2 to 4 inches, Z may be made from inch to 1inches.

The following voltages, measured with respect to cathode, have beenfound to give satisfactory results for the 14-inch tube.

Cathode (16) -40 volts Preaccelerator (22) +5000 volts First anode (29,29a) +1500 volts Second anode (30) +5000 volts Deflection plates +5000voltsirespective signal voltages Electrode 58 +l0,000 volts Electrode 59+5000 volts The ed e 58a of the electrode 58 may be disposed a distanceof about an inch from the edge 9a of the screen 9.

It is possible with my improved tube, embodyv ing the structuralfeatures and using the relations and values given above, to employ anextremely high accelerating voltage in order to get a very intense traceor picture, and still deflect the ray to cause the same to scansubstantially the entire area of the screen 9, since the deflectionsensitivity is only reduced by approximately 18%. as against about 50%reduction in the cathode-ray tubes of the prior art, should the finalaccelerating voltage be doubled.

It has been found that when the distance from the edges 49 to the edge59a of electrode 59 is too great, electrostatic fields are set up suchthat the useful area of screen 9 is reduced as a strong function of theratio of potentials on electrodes 58 and 59. In addition to thereduction of possible, effective screen area, a radial distortion isintroduced, and the outer ends of normally straight lines off the axisare caused to return toward or through the axis of the tube.

On the other hand, when the distance from 49 to 59a is too small, theelectrostatic lines of force that would normally terminate in 59 toproduce a spherical field within the intervening space, terminateinstead on the deflection plates 33 and, to some extent, on thedeflection plates 36. As a result, the accelerating field in that spaceis no longer spherical and produces a distortion of the fluorescentspot. Thus a normally round spot would become elliptical with its majoraxis parallel to the edges 49.

The electrode 58 may be a coating of colloidal graphite known asAquadag" and a terminal coating 58b of silver which contacts or overlapsthe Aquadag coating at 580. The electrode 59 is a silver coating.

Spot-welded to the electrode 30 is a metal disc 3! provided with thecircular openings shown in Figs. 3 and 4, and with a mica-disc insert32. The disc 6| acts as a conducting shield for 001- lecting strayelectrons which otherwise would form or set up a halo on the screen 9 inthe absence or presence of signal voltage. Such a halo, when signal ispresent, would reduce contrast. The diameter of the shield 6! .isrelatively large, so that its edge is in close proximity to the wall ofthe neck of the tube.

A whisker 6 la spot-Welded to the shield and spring-biased outwardly tocause engagement of its free end with the electrode 59 providesconnection between the latter and the shield.

The adjacent ends of ceramic rods I, 2, 3 and 4 abut the mica disc 32,and are secured to electrode30 by the straps 30c, 30d, 30c and 3M.

The part 29a of the focusing electrode is secured to the ceramic rods bythe straps 29b and 29c (Fig. 6).

The part 29 of the focusing electrode is secured to the ceramic rods bythe straps 29d and 29e.

The electrode 22 is secured to theceramic rods by the straps 22a.

The electrode 20 is secured to the ceramic rods by the straps 20a, 20band the complementary pieces 200.

The cathode I 6 is supported by a short piece of wire Ilia spot-weldedto one of the straps l6b secured to the ceramic rods.

. The cathode-heater is supported by having its terminals I6espot-welded to the short pieces [5 of wire which are spot-welded to therespective terminal wires l6 and I6" extending through the press.

With regard to the supporting wires 33a, 33b,

33c and 33d for the deflecting plates 33, the wires welded to the wire36a.

33a and 330 terminate at the mica disc 32, but the wires 33b and 33dcontinue through the mica disc 24 to the respective terminal wires 33!)and 3311' which extend through the press.

With regard to the supporting wires 36a, 36b,

36c and 36d for the deflecting plates 36, the wires 36b and 36dterminate at the mica disc 32, but the wire 36a continues to andterminates at the mica disc 24, and the wire 360 extends through disc 24and is spot-welded to the terminal wire 36c extending through the press.

An important feature of my improved tube resides in the means for makingconnection to the intensifier electrode 58. This comprises a coaxialcable made up of a wire 58f extending through a glass tube 589 which isbent as shown, and is provided with an outercoating 58h. of silver. Asshown in Fig. 10, one end of the wire 58f makes contact with the silvercoating 58!). The other end of the wire 58) is spot-welded to a shortpiece of wire 58k Fig. 8 which is spotwelded to one end of an L-shapepiece 581'. The other end of the piece 587' is spot-welded to theterminal wire 58 which extends through the press. The tube 589 extendsloosely through the shield GI and the mica discs 32 and 24, and thesilver coating 58h makes electrical contact with the shield 6|. Wheninserting the entire press assembly into the tube blank, the bent glasstube 58g is placed in the position shown in Figs. .1 and 2, so that itclears. The tube 589 is then rotated through degrees and moved axiallyso that its bifurcated end portion 581' straddles and interlocks withone leg of the L-shape piece 587, as shown in Fig. 1a and as indicatedby dash-line in Fig. 8. When the gun and press assembly are fullyinserted into the neck of the tube, therefore, the tube 589 is in theposition shown in Fig. 10 and the free end of the wire 58 engages thesilver coating 58b.

One end of the connection 42 is spot-welded to the shield 6|, and theother end extends through disc 24 and is spot-welded to the wire 22b.One end of the wire 22b is spot-welded to the straps 22a, and the otherend is spot-welded to the terminal wire 22' extending through the press.

Connection with the electrode 20 is made by a piece of. wire 20dspot-welded to the straps 20a and to the terminal wire 20 extendingthrough the press.

Connection with the cathode I6 is made through a piece of wire l6cspot-welded to the straps I61) and to the terminal wire I6.

'One end of a connecting wire 36m is spot- The wire 36:): passes throughthe disc 24 and is spot-welded to the terminal wire 36a.

A connecting wire 29d is spot-Welded to the straps 29c and 29d. The wire29d passes through the disc 24 and is spot-welded to the terminal wire29'.

From the foregoing it will be seen that connection to the intensifierelectrode 58 is made by the terminal 58'. Connection to electrode 59,shield BI, and electrodes 30 and 22 is made by the terminal wire 22'.Connection to electrode 20 is made by the terminal wire 20'. Connectionto the cathode l6 and one side of the cathodeheater is made by theterminal wire i6, and connection to the other side of the cathode-heateris made by the terminal wire it". Connection to electrode 29, 29a ismade by the terminal wire 29'. Connection to the plates 33 is made bythe terminal wires 33b and 33d. Connection to the plates 36 is made bythe terminal wires 36a and 380'.

By making connection with the intensifier electrode 58 through thepress, by means of the coaxial cable, the old tip or protrusion on thebulb for this purpose is eliminated. Also. all hightension leads areautomatically connected when the bulb is plugged into the sockettherefor.

Another important detail of my improved construction resides in themeans for assembling and securing together the deflecting plates and therespective supporting wires therefor. For example, and with referenceparticularly to Figs. 1, 2 and 3, the ends of the wires 36a and 38b forsupporting the associated deflection plate are placed against thisplate, and upon these ends is placed the strap 38c of sheet metal andhaving the stamped-out portions shown, to receive these ends. Thesecuring strap lies flush against the deflection plate, and isspot-welded thereto and to the ends of the supporting wires. As shown,the ends of the supporting wires are sandwiched between the deflectionplate and the strap 36c, and by reason of the stamped-out portions ofthe latter, the strap functions as a gauge for quickly and convenientlyspacing and positioning the ends of the supporting wires properly andensuring correct alignment of the parts and uniformity of construction.As shown in the drawings, the other deflection plates and the respectivesupporting wires therefor are secured together by similar straps, in thesame way. Reenforcing pieces, such as 33', join the pairs of adjacentsupporting wires for the deflecting plates.

With reference to Figs. 4a. and 4b, the wire 36c passes through agrommet 32a having the portions 32c riveted over onto the mica disc 32,and the portions 32c spot-welded to the wire 360. The distance from thegrommet to the edge 32b provides suflicient insulation between theshield .6i and wire 360. Similar grommets are used for the other wireswhich pass through or terminate at the mica discs 32 and 24.

It will be understood that various modifications within the conceptionof those skilled in the art, are possible without departing from thespirit of my invention or the scope of the claims.

I claim as my invention:

1. In a cathode-ray tube, a tube having a screen at the end wallthereof, said tube at the end thereof opposite said screen beingprovided with a press, a gun supported by said press and disposed insaid tube for developing a ray of electrons directed at and focused onsaid screen, deflecting means for said ray of electrons in said tube, anelectrode extending along said tube and beyond said deflecting means inthe direction toward said screen, a second electrode disposed betweensaid first-named electrode and said screen for minimizing defocusing ofthe ray-spot on said screen and for minimizing reduction of deflectionsensitivity, said second-named elect r ode being adapted to operate at apotential higher than the potential of operation of said first-namedelectrode, and connection means comprising a conductor extending throughan elongated insulator having conducting material on the outsidethereof, said conductor engaging said second-named electrode andextending along said tube within the same and through said press toprovide exteriorly of said tube at said press a terminal for applicationof potential to said second-named electrode.

2. In a cathode-ray tube, a tube having a screen at the end wallthereof, a gun disposed in said tube for developing a ray of electronsdirected at and focused on said screen, a press supporting said gun,means for deflecting said ray to cause the same to scan said screen. anelectrode extending along said tube and beyond said deflecting means inthe direction toward said screen, a second electrode disposed betweensaid screen and said first-named electrode, said second electrode beingadapted to operate at a potential positive with respect to the potentialof operation of said first-named electrode, the diameter of said tube ata plane in proximity to said screen being substantially greater than themaximum effective diameter of said screen, and connecting meanscomprising a conductor extending through an elongated insulator havingconducting material on the outside thereof, said conductor extendingfrom said second electrode and along said tube within the same andthrough said press to provide exteriorly of said tube at said press aterminal for application of potential to said second-named electrode.

3. In a cathode-ray tube, a tube having a screen at the end wallthereof, said tube at the end thereof opposite to said screen beingprovided with a press, a gun supported by said press and disposed insaid tube for developing a ray of electrons directed at and focused onsaid screen, means for deflecting said my to cause the same to scan saidscreen, an electrode extending along said tube and beyond saiddeflecting means in the direction toward said screen, a second electrodedisposed between said first-named elec trode and said screen forminimizing defocusing of the ray-spot on said screen and for minimizingreduction of deflection sensitivity, said second-named electrode beingadapted to operate at a potential higher than the potential of operationof said first-named electrode, and coaxialcable means engaging saidsecond-named electrode and extending along said tube within the same andthrough said press to provide exteriorly of said tube at said press aterminal for application of potential to said second-named electrode.

4. In a cathode-ray tube, a tube provided with screen structure and witha gun for developing a ray of electrons directed at said screenstructure, a pair of plates for deflecting said ray, at least one ofsaid plates being supported by wires whose ends are disposed against oneside of said plate at an edge thereof and are perpendicular to saidedge, and a strap disposed against said ends and flush against saidplate at said edge thereof and secured to said plat and said ends,

said strap being pressed out to receive and accommodate said endswhereby said strap initially can function as a gauge to space andposition said ends with respect to said plate prior to the securing ofsaid parts together.

5. In a cathode-ray tube, a layer of conducting material on the insideof said tube between the gun and screen of said tube, means forsupporting an electron gun in said tube, and an elongated insulatorcarrying an electrical conductor to contact with said layer ofconducting material, said insulator and conductor being bent andrevoluble with respect to said tube to provide contact of said conductorwith said layer of insulating material.

6. In a cathode-ray tube, a layer of conducting material on the insideof said tube between the gun and screen of said tube, means forsupporting an electron gun in said tube. an electrical conductor tocontact with said layer, an insulating supporting member for saidconductor, and a conducting electrical shield on a portion of saidmember to prevent the electric field 0! said conductor from distortingthe electron beam between the gun and the screen.

7. In a cathode-ray tube, a layer of conducting material on the insideof said tube between the gun and screen of said tube, means for sup- 10porting an electron gun in said tube. an electrical conductor to contactwith said layer, an insu-' lating supporting member for said conductor,and a conducting electrical shield on a portion of said member toprevent the electric field of said conductor from distorting theelectronbeam between the gun and the screen, said member being bent andrevoluble and means to locate and secure said member in its operatingposition. STANLEY J. KOCH.

